In an automated information storage and retrieval system, also known as an automated library, numerous slots, or storage cells, are arrayed within the library. These storage cells are used to hold information media that are portable or removable from the library, such as magnetic tape cartridges or optical disks. The term "cartridge" used herein refers to any structure for housing such removable information media. Although the present invention is described herein with respect to an optical library storing optical disk cartridges, it is not so limited but is equally applicable, for example, to a library holding magnetic tape cartridges, optical tape cartridges, magnetic disk cartridges or diskettes, or the like. The storage cells typically have an opening in the front to allow the cartridge to be inserted or removed.
A library typically includes a controller, an accessor, a drive, and an Input/Output station. The library controller directs the actions of the other library components. The library controller can also connect to a host processor and respond to control commands from the host processor. The library controller inventories the storage cells noting the identity of each cartridge occupying a storage cell. If no cartridge is situated in a particular storage cell, the library controller records this storage cell as empty. Typically, each cartridge has a unique identifying mark, such as a bar code label, on an edge of the cartridge visible through the cell opening.
The accessor transports a selected cartridge between its origin and its destination. A storage cell, a drive, and the Input/Output station serve as origins and/or destinations. The accessor grips the cartridge with a holding device. The accessor may also be equipped with a vision system, such as a bar code reader, to read the label on a storage cell when the accessor is positioned near the storage cell. During an inventory of the library, such as when a new library has been installed, the vision system scans the cells and reports to the library controller the identity of stored cartridges and their location within the array of storage cells. Alternatively, in a library without a vision system, each cartridge must be loaded into a drive whereby the identifying information is read. The cartridge is then returned to a storage cell. The library controller records the identity and location information in a database. The library controller later refers to and updates this database when a cartridge is moved between an origin and a destination. In this sense, the library controller must "know" the identity of each cartridge and its location within the array of cells in order to be able to retrieve the cartridge for access.
Libraries also have one or more drives to read data from a cartridge or write data to a cartridge. The accessor removes a selected cartridge from a storage cell and inserts it into the drive. Once in the drive, data can be read from the cartridge and sent to the host processor. In some library configurations, the data is sent to the host processor through the library controller, whereas in other library configurations, the data is transferred directly from the drive to the host processor. In this latter configuration, the library controller sends a response to the host processor indicating the selected cartridge is placed in the drive. The host processor then issues a command to the drive to transfer the data. Likewise, data can be written from the host processor to the drive in either library configuration. In both configurations, the library controller directs the accessor to load the selected cartridge into the drive before the data is written to the cartridge.
Libraries also typically include an Input/Output station and an operator panel. The Input/Output station is a port through which a system operator can pass a cartridge to be added to the storage array or through which the accessor can pass a cartridge to the operator for removal from the storage array. The operator panel provides a communication mechanism for an operator to make requests to add cartridges to the library or remove cartridges from the library. The Input/Output station allows the operator to change cartridges in the storage array without requiring the library controller to inventory the entire storage array. Typically, an inventory must be taken each time a library access door is opened by the operator since it is not known whether the operator has added cartridges to the array, has removed cartridges from the library, or has not altered the contents of the library at all. The term library access door refers to a door in the library large enough to allow the operator to manually insert or remove cartridges into the storage cells of the storage array. The library access door does not refer to a door which provides the operator access to the Input/Output station.
When the library needs to be moved from one location to a separate location, the cartridges currently must be removed from their respective storage cells. Otherwise, the cartridges could fall from their storage cells when subjected to the forces of repositioning the library and to the vibrations resulting from the transportation of the library. The risk of falling cartridges occurs from either moving the library a short distance, such as another position within the same room, a medium distance, such as another building within the same site, or a long distance, such as another site.
Furthermore, library manufacturers currently cannot insert cartridges into their respective storage cells at the manufacturing site before shipment to a customer because of the risk that many cartridges would fall from their storage cells during transportation of the library to the customer. Instead, the libraries are shipped to the customers with the storage cells empty of cartridges. The manufacturers must wait until the library has been delivered to the customer and positioned within the customer's facility before inserting the cartridges into the storage cells. Manual insertion of the cartridges becomes part of the library installation procedure at the customer site and lengthens the time before the library becomes available for use by the customer. Thus, library manufacturers would prefer to fill the storage cells of the library with cartridges at the manufacturer's site before shipping the library to the customer to reduce the library installation time at the customer's site.
Additionally, those who own or use libraries face problems when they need to move the library. The risk of cartridges escaping from their respective storage cells when transporting the library forces these owners and users to remove the cartridges before moving the library. To remove the cartridges from the storage cells, an operator must open the library access door. Once the library is moved to its new location, the operator must again open the access door and return the cartridges to the storage cells. Thus, moving the library from one location to another compounds the problem faced by the manufacturer installing the library at the customer's site. In the case of moving the library, the owner/user must both remove the cartridges from the storage cells and then re-insert the cartridges into the storage cells requiring twice the time and effort.
A new inventory must then be taken of the cartridges and their storage cell locations once the library is repositioned in its new location. The new inventory is triggered by the operator opening the library access door to remove the cartridges prior to moving the library. As stated earlier, an inventory of all the storage cells in the library can be a time-consuming task.
Libraries equipped with a vision system on the accessor can perform an inventory of the library more quickly than those libraries not equipped with a vision system. In these libraries, the vision system of the accessor scans all the storage cells in the storage array and reports to the library controller the identity of stored cartridges and their location within the array of storage cells. If a cartridge label cannot be detected or read when the accessor is near a storage cell, that cell is recorded as empty. The vision system may also mistakenly classify a cell as being empty when, in fact, the cell is actually occupied. For example, a cartridge may occupy the cell but have an unreadable label, or even no label. A cartridge may be improperly oriented within the cell or a foreign object may occupy the cell. If the accessor attempts to insert a cartridge into such an occupied cell, an error condition will result causing a time consuming error recovery procedure to be initiated.
One known error procedure attempts to reduce such non-empty errors by directing the accessor's gripper to attempt to reach inside every cell which does not have an identifiable cartridge and verify by "touch" that the cell is actually empty. Any cell which is still not found to be empty is classified in the database as having an "occupied but invalid" status to prevent its use. An inventory of a 400 cell library, for example, can take three or four hours to complete using this procedure.
Libraries not equipped with a vision system must perform an inventory of the library by reading the cartridge identity from the information stored on the cartridge. In these libraries, the accessor transports a cartridge from its storage cell to a drive. The drive reads the identity of the cartridge from the header information stored within the cartridge. The identity of the cartridge and the location of its corresponding storage cell is reported to the library controller. The library controller records the identity and location information in a database. The library controller then signals the accessor to move the inventoried cartridge from the drive to its storage cell within the storage array. The process is then repeated for each storage cell within the storage array.
Accordingly, a retainer system is desired within the library to prevent the cartridges from escaping the storage cells when the library is moved. By holding the cartridges within their respective storage cells, the retainer system enables a library owner/user to move the library from one location to another without removing the cartridges. The library owner/user saves the time it takes to remove the cartridges from the storage cells and the time it takes to re-insert the cartridges into the storage cells. For a large library, this can be a significant delay. A retainer system also enables a library manufacturer to preload the storage cells of the library with cartridges before shipping the library to a customer. Delivering the library loaded with cartridges significantly reduces the time to install the library at the customer site making the library available to the customer much earlier.
In addition, a retainer system that can be engaged without opening the library access door may save the time required to perform an inventory of the library storage arrays. As stated earlier, opening the library access door triggers an inventory of the library storage cells. If the retainer system can be activated to hold the cartridges in their corresponding storage cells without opening the library access door, an inventory is not necessary when the retainer system is later deactivated.
Most libraries, including most optical disk libraries and many magnetic type libraries, need not perform an inventory of the storage array after the library has been powered off and subsequently powered back on. These libraries (hereinafter denoted enhanced libraries) save the inventory information in a memory unaffected by the power loss to the library. One example of these enhanced libraries stores the inventory information in a non-volatile storage contained in the library and accessible by the library controller. When this type of library loses power, the non-volatile storage maintains power through a battery and the inventory information is retained until power to the library is restored. Another example of these enhanced libraries transfers the inventory information to a host processor where the information is stored in a memory in the host processor. The inventory information in the host processor memory is unaffected by a power loss to this type of library.
These enhanced libraries must also determine whether the access door was opened after the library has been powered off. If the library access door is opened during the time the library was powered off, the library must perform an inventory when power is restored. Otherwise, an inventory is not necessary when the library is powered back on. Thus when these enhanced libraries need to be moved, a retainer system that is activated without opening the library access door can save the time required to conduct an inventory of the library storage cells in addition to the time required to remove and re-insert the cartridges within the storage cells.
The retainer system of the present invention accomplishes the two objectives mentioned above. It holds the cartridges within their respective storage cells and prevents their escape therefrom. Further, the retainer system activates the retaining means without requiring the library access door to be opened.